Facts About Menstruation and Pain : Menstruation, or commonly known as periods, is the body’s way of getting rid of what it doesn’t need. Around once a month, the lining of the uterus thickens in preparation for a fertilized egg – should the woman become pregnant.

When that doesn’t happen, that lining and a small amount of blood passes through the vagina. This monthly process is a natural normal part of female living.